This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPP third generation partnership project
A-FLT advanced forward link trilateration
BSR buffer status report
CQI channel quality indicator
DL downlink (eNB towards UE)
DM RS demodulation reference signal
eNB EUTRAN Node B (evolved Node B)
E-OTD enhanced observed time difference
EPC evolved packet core
E-UTRAN evolved UTRAN (LTE)
FCC Federal Communications Commission
GPS global positioning system
GSM global system mobile
LCS location services
LE locating entity
LMU locationing measurement unit
LTE long term evolution
MAC medium access control
MM/MME mobility management/mobility management entity
Node B base station (also eNB)
O&M operations and maintenance
OFDMA orthogonal frequency division multiple access
PDCP packet data convergence protocol
PHY physical
PRACH physical random access channel
PUSCH physical uplink shared channel
RLC radio link control
RRC radio resource control
SC-FDMA single carrier, frequency division multiple access
S-GW serving gateway
SPS semi-persistent scheduling
SRS sounding reference signal
TTI transmission time interval
UE user equipment
UL uplink (UE towards eNB)
U-TDOA uplink time difference of arrival
UTRAN universal terrestrial radio access network
WCDMA wideband code division multiple access
A communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA) is currently under development within the 3GPP. As presently specified the DL access technique will be OFDMA, and the UL access technique will be SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.6.0 (2008-09), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Overall description; Stage 2 (Release 8).
FIG. 1 reproduces FIG. 4.1 of 3GPP TS 36.300, and shows the overall architecture of the E-UTRAN system. The EUTRAN system includes eNBs, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE. The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME (Mobility Management Entity) by means of a S1 MME interface and to a Serving Gateway (S-GW) by means of a S1 interface. The S1 interface supports a many to many relationship between MMEs/Serving Gateways and eNBs.
The eNB hosts the following functions:                functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling);        IP header compression and encryption of the user data stream;        selection of a MME at UE attachment;        routing of User Plane data towards the Serving Gateway;        scheduling and transmission of paging messages (originated from the MME);        scheduling and transmission of broadcast information (originated from the MME or O&M); and        a measurement and measurement reporting configuration for mobility and scheduling.        
The technology to locate mobile devices is gaining ground and the development of these technologies is in part driven by the United States Federal Communications Commission (FCC) emergency call requirements, where a terminal placing an emergency call must be positioned with a 67% probability within 50 meters and with a 95% probability within 150 meters. A GPS system could provide such accuracies when the satellites are visible to the receiver, but in indoor/urban environments the probability of determining a GPS position is not high enough to meet these requirements. Additional solutions are needed.